Arc decreasing circuit



9, wxanzmmmg ARC DBCREASING CIRCUIT Filed Sept. 30, 1942 2 Sheets-Sheet l I N V EN TOR. 5220mm} 3. WILLIAMS.

vA'!"I'URNEY Oct. 9, 1945. s. B. WILLIAMS 2,386,377

ARC DECREAS ING CIRCUIT Filed Sept. 50, 1942 2 Sheets-Sheet 2 lid 0N5 Y B. mLL IA M5 ATTO I EY Patented Oct. 9, 1945 ARC DECREASING CIRCUIT Sidney B. Williams, West Caldwell, N. J., assignor to Jrn'tiss-Wright Corporation, a corporation of Delaware Application September 30, 1942, Serial No. 460,307

2' Claims. (Cl. 170-163) My invention relates to a circuit arrangement for decreasing the arcing effect at a pair of switch contact members when the flow of electrical current therethrough is interrupted.

More particularly, my invention relates to a system including an electrical motor and an energizing source of electrical current, relatively movable switch contact members being provided for interrupting the flow or" current to said motor, the system including means, such as a rectifier, connected across a winding of the motor for decreasing the arcing effect at said contact members when one of them is separated from the other to open the circuit of said motor.

Various other objects, advantages and features of my invention will become apparent from the following detailed description.

My invention resides in the circuit arrangement, arc-decreasing means, features and arrangements of the character hereinafter described and claimed.

For an understanding of my invention and for an illustration of one of the forms thereof, reference is to be had to the accompanying drawings, in which:

Figs. 1 and. 2 are diagrammatic views illustrating the invention; and

Fig. 3 is a sectional View showing a limit switch arrangement.

Referring to Figs. 1 and 2, I have diagrammat ically illustrated parts of a power unit and power gear assembly for controlling the pitch of an airplane propeller as manufactured by Curtiss- Wright Corporation. in Fig. l, I have shown the adapter plate 3 which is disposed at one end of the housing l and, in Fig. 2, I have shown the flange 3 the propeller huh the adapter plate 5 and the it being adapted to be suitably securedtogether to form a unitary assembly.

The housing contains the motor which, either automatically or under manual control, operates to change the pitch oi the associated propeller, the operating circuits of this motor being enclosed by said housing and terminating in the contact members cl, c2, and ct, the contact members cl, c3 and o l being movable as hereinafter described.

This arrangement has been diagrammatically illustrated in Fig. 1 wherein the contact mern- :ber cl is shown as having connected thereto a conductor 5 which extends to one terminal of the motor M and includes one of the motor field windings 6. Branching from the conductor between the contact member cl and the field winding 6, is aconductor l which extends to the contact member 04. The contact member 02 has connected thereto a conductor 8 which extends to the other terminal of said motor M, the conductor 8 including a coil 9 which serves as an electro-magnetic winding for releasing aspringactuated brake simultaneously as the motor M is energized. The contact'member at has con nected thereto a conductor l9 which leads to the aforesaid conductor 5, said conductor 50 including the other motor field winding ii.

The hub carries the fixed contact members lcl, k2, k3 and M with which the aforesaid contact members cl, c2, c3 and 04 are coactable respectively. These fixed contact'members of the hub 4 have conductors connected thereto, respectively, these conductors being carried by said hub 4 and leading to sources of electrical current, sets of relay contact members and a switch all disposed exteriorly of said assembly.

This arrangement has been diagrammatically illustrated in Fig. 2 wherein the contact member lcl is shown as having connected thereto a conductor if: which leads to one terminal of a manually operable switch it, said conductor 52 including a booster motor-generator or dynamotor l5 hereinafter termed a booster motor. The contact member k2 has connected thereto a conductor it which leads to the other terminal of the aforesaid manually operable switch it, said conductor it including a battery Broaching from the conductor between the contact mem her Fe? and the battery is a conductor its which leads to the booster motor i l. The con members R3 and id? have connected thereto the respective conductors and which oerminate, respectively, in fixed contacts with which are coactaole movable contacts forming, respectively, the terminals of conductors and 29 which have coruiected thereto conductor which leads to and is connected to the aio said conductor between the switch and the battery The movable contacts and the associated conductors and 263 constitute a pivoted structure which may be actuated to swing in a clockwise direction, in response to energization of a relay winding to connect the conductors and together, or in a counterclockwise direction, in response to energization of a relay winding to connect the conductors i8 and 20 together. Energization of these windings is effected individually by an automatically controlled switch When the adapter plate l and the hub l have been connected together to form the unitary assembly described above, the movable contact members cl, c2, c3 and o l coact, in circuit-iormin elation, ith the respective contact members 2115, It! 553 and ic i.

When the airplane carrying the disclosed pow or unit power gear assembly is in flight and the speed of the airplane engine changes such'manner that the pitch of the airplane propeller should be increased, the relay winding is-energized to cause the contact at the end or the conductor to engage the adjacent contact at the end or the conductor When this happens, a circuit is completed as follows: From the negative terminal of the battery it by way of conductor it, contact members 2'02 and 02, con

ductor i3 including the coil the motor M, conductor 5 including the winding conductor 3, contact members ed and led, conductor i8, con ductor 2t, conductor 29, and thence back o the positive terminal of said battery it by way of the conductor i5. Closure this circuit effects operation of the motor M in such direction that the pitch of the airplane propeller increases.

In the event that the speed of the airplane engine changes in such a manner that the pitch of the airplane propeller should be decreased, the relay winding 22 is energized to cause the contact at the end of the conductor it to engage the adjacent contact at the end oi the conductor ll. When this happens, a circuit is completed as follows: From the negative terminal of the battery it by way of the conductor 5, contact members I02 and c2, conductor 8 including the coil 9, the motor M, conductor 5, conductor ill including the winding ll, contact members 63 and k3, conductor ll, conductor is, conductor 2 l, and thence back to the positive terminal of the battery it by way of the conductor l5. Closure of this circuit efi'ects operation of the motor M in such direction that the pitch of the airplane propeller is decreased.

In the event that the operation of the airplane engine is discontinued during flight and, if the airplane propeller is to be moved to feather position, the pilot closes the switch i3 to thereby close a local circuit through the booster motor ill and the battery I 6. As a result the booster motor Ml supplies current over a circuit as fol-= lows: From one output terminal of said booster motor it by way of the conductor 5 5a,, conductor i5, contact members E2 and c2, conductor 83 in= cluding the coil 9, the motor M, conductor 5 including the winding 5, contact members cl, and Fri, and thence back to the other output terminal of said. booster motor i l by way of the conductor it.

In view of the foregoing description, it will be understood that the contact members 02, k2 remain closed at all times. The other sets of contact members constitute limit switches in the respective feather, low pitch and high pitch cir cuits of the assembly herein described. That is, the contact member cl moves from the associated contact member kl when the airplane propeller has moved to maximum extent in feather positlon; the contact member c3 moves from the associated contact member k3 when the airplane propeller has moved to maximum extent in lowpitch position; and the contact member c 3 moves from the associated contact member fail when the airplane propeller has moved to maximum extent in high pitch position. In each instance, the aforesaid movable contact members are moved by suitable mechanism as known to those skilled in the #:rf or Quentin assembled described. the propeller movable ovaole con- .cber suit locatory moveccntact member .i 2o using actuatabi by movable connected. thereto. The member is disposed within a member 2? fixed to the housing As illustrated, the contact members cl and Fri are enclosed by telescopically arranged sleeves 22 and formed suitable electricity-insulating material.

In connection the invention, it will be understood that the construction and arrangement the sets of contact members c3, E03 and o l, ad is the same as described above as regards contact members oi lei The battery iii described above, which operates the high pitch and low pitch circuits, has a voltage if twenty-four volts, for example, whereas the booster motor to de scribed above, which operates the feather circuit, has a voltage of ninety-six volts, for example. When any one of the contact members cl, c3 or ad, particularly, the former which is the high voltage circuit, is moved to circuit-opening position, the inductive surge of current usually strikes an arc and this, of course, results in damage to the contact members included in the deenergized circuit.

In accordance with my invention, this undesired arcing effect is entirely or largely prevented by connecting a suitable unilateral device such as a dry disk or other current rectifier across each of the field windings 6 and H and also across the motor M together with the brake coil 9. Thus, as shown in Fig. 1, one terminal of a unilateral device such as a suitable rectifier R is connected to the conductor 5 between the Junction thereof with the conductor l and the field winding 6 while one terminal 'of another similar rectifier BI is connected to the conductor it between the contact member c3 and the field winding ii. The other terminals of these rectifiers are connected ably" mounted for: a torrent with respect ici said movable mer together by a conductor 30 which extends across When this happens, the interrupted field current then flows along the alternate path which includes the motor field winding 8, the motor armature, the brake coil 9 and the-rectifier R thus tending to maintain the field excitation. The resultant slower decay of current in the field winding 8 produces a smaller inductive surge with consequent less tendency to strike an are at the contact members 0!, ki Further, the motor armature counter voltage is maintained longer due to the slower decay of field current as noted above and this counter voltage opposes the voltage tending to strike the described arc. In this manner, the inductive surge is dissipated due to-the presence of the rectifier R, the latter, however, during normal operation being inefiective to cause the use of more current.

It will be understood that'the action of the limited. As desired, said rectifiers R and Hi rectifier R is the same as described above when the motor M and the field winding e are energized from the battery 55 to increase the propeller pitch. Further, it will be understood that the action of the rectifier R! in the circuit of the field winding ii and motor M corresponds with that of the rectifier R.

Although I have illustrated and described the rectifiers R and Bi as connected across the field windings, the motor and the brake coil, it will be understood that the invention is not to be thus may be connected across the field windings, the motor and the brake coil separately or jointly as de sired. When said rectifiers R, and Hi are connected solely across the respective field windings, the fiow of field current to be maintained will not be opposed by the desirable counter voltage of the motor armature. This is a desired arrangement.

In accordance with the invention, it is desirable that the connection of the rectifier or reotifiers in circuit relation should not necessitate the use of additional sets of contact members cl, kl, etc. With the forms of the invention herein disclosed, this desirable object is attained and, as will be understood, said rectifier or rectifiers may be carried by the housing 2 or otherwise as may be desirable.

With the circuit herein illustrated, the normal pitch-changing operation occurs automatically as described. Other circuits may be used as desired to effect this operation. Further, for manual control of normal changes in pitch, known circuits may be used in lieu of the one illustrated. With all of these circuits, the arrangement of the invention serves to decrease the are at the pair of contact members which function as a limit switch. Obviously, said arrangement of the invention also protects any other switch or relay contacts which are included in the circuit.

While the invention has been described with respect to a certain particular preferred example which gives satisfactory results, it will be understood by those skilled in the art after understanding the invention, that various changes and iii modifications may made without from the spirit and scope oi the is intended therefore in the app ecover all such changes and modifications;

What is claimed as new and desired to be secured byLetters Patent is:

i. In combination, means comprising a motor housing and a propeller hub detachably secured to each other, cooperative fixed and movable switch contact members forming a part of said assembly, electrical conductors carried by said housing for connection to a motor and its field winding, conductors carried by said propeller hub for connection to a source of electrical current and a control means, one of said first named conductors terminating in one of said contact members, one of said second named conductors terminating in the other of said contact members, and means for decreasing the arcing effect at said contact members when said movable contact member is separated from said fixed contact member, said last named means comprising a rectifier disposed in parallel relation with respect to said field winding, the terminals of said rectifier being connected to said first named conductors and said rectifier being carried by said housing.

2. In combination, means comprising a motor housing and a propeller hub detachably secured to each other, cooperative fixed and movable switch contact members forming a part of said assembly, electrical conductors carried by said housing for connection to a motor and its field winding, conductors carried by said propeller hub for connection to a source of electrical current and a control means, one of said first named conductors terminating in one of said contact members, one of said second named conductors terminating in the other of said contact members, and an electrical device for decreasing the arcing eilect at said contact members when said movable contact member is separated from said fixed contact member, the terminals of said electrical device being connected to said first named conductors.

SIDNEY B. WILIJLAMIS. 

